With the ceaseless increasing of size of a display and the ceaseless raising of frequency of a driving circuit, it has become difficult for mobility of an existing amorphous silicon thin film transistor to meet the demands.
As regards high-mobility Thin Film Transistors (TFTs), there are polycrystalline silicon TFTs and metal oxide TFTs. However, polycrystalline silicon TFTs have poor uniformity and a complex manufacturing process, and they are limited by laser crystallization equipment and the like, which counts against large-scale production. While metal oxide TFTs being transparent possess a high mobility, good uniformity, and a simple manufacturing process, and can meet the demands of large-size Liquid Crystal Displays (abbreviatedly referred to as LCDs), Organic Light Emitting Diodes (abbreviatedly referred to as OLEDs) and Polymer Light Emitting Diode displays (abbreviatedly referred to as PLEDs) better, and thus, they get a wide attention.
Under normal circumstances, in terms of a thin film transistor, a certain energy barrier may be formed on contact surfaces between source and drain electrodes and a semiconductor active layer, so as to form contact resistances; and the energy barrier can hinder the motion of carriers. When the energy barrier at the interface is larger and Schottky contact is formed, it easily brings about the loss of signal, and thus performance of TFTs is affected.
In addition, in the course of manufacture of an existing metal oxide TFT, a subsequent manufacturing process may cause damage to a metal oxide semiconductor active layer, resulting in deterioration of the performance of the TFT.
Therefore, how to guarantee the performance of TFTs is very important.